Multimedia multiplexing method

ABSTRACT

A multiplexing method for multimedia communication is provided, which is compatible with the H.223 protocol by changing a header of a multiplex protocol data unit (MUX-PDU). The multiplexing method includes the steps of encoding media data, and multiplexing the media data encoded in the step (a) in units of a predetermined frame, and inserting a second flag having a predetermined length with an auto-correlation in the frame after a first flag having the opening and closing of the frame. Therefore, the probability of detecting the MUX-PDU by a receiver is increased by adding a flag having a high auto-correlation to the H.223 MUX-PDU frame, thereby increasing error-resiliency.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a multiplexing method formultimedia communication, and more particularly, to a multiplexingmethod compatible with the H.223 protocol by changing a header of amultiplex-protocol data unit (MUX-PDU).

[0002] In general, the H.324 recommendation prescribes a multiplexing ofvideo and audio signals which is effective in an error-prone channelsuch as a wireless channel, and includes H. 223 multiplexing, H.245controlling, H.263 video CODEC and G.723.1 audio CODEC. Also, H.223multiplexing is recommended as a method for multiplexing video, audioand other data in protocol data units (PDU) in order to realize a videotelephone and video conferencing in a total digital telecommunicationnetwork by the ITU-T (the telecommunication standardization sector ofthe International Telecommunication Union). Also, the M.324recommendation includes Mode 1 having high complexity and Mode 3 withouthaving complexity. According to the Mode 1, while generating a variablelength packet an unequal error protection (UEP) is performed by adoptinga rate compatible punctured convolutional (RCPC) encoder/decoder (CODEC)in an adaptation layer which is an upper layer. Also, an automaticrequest for retransmission (ARQ) is used to maintain the overall qualityof service (QOS) even though the channel throughput decreases. However,the Mode 1 has a high complexity at a portion of RCPC CODEC, whichincreases the complexity of the overall system. Thus, it is difficult toimplement a real-time process. Also, the total channel throughput of thesystem may decrease rapidly since it adopts a retransmission method. Forexample, the channel throughput is 50% or less when the retransmissionis performed one time, and 33% or less when the retransmission isperformed twice. Thus, it is difficult in Mode 1 of the H.324 toimplement transcoding having compatibility with the conventional H.223.Meanwhile, Mode 3 has virtually no error-protection concept, so thaterror-resiliency in an error-prone channel is very low.

SUMMARY OF THE INVENTION

[0003] It is an object of the present invention to provide amultiplexing method for multimedia communication, enabling transcodingwith the H.223 protocol by adding a flag which is similar to a pseudonoise code (PN CODE) after a high-level data link control (HDLC) flag inthe multiplex-protocol data unit (MUX-PDU) by the H.223 protocol.

[0004] To achieve the object, there is provided a multiplexing methodfor multimedia communication in the H.223 protocol, comprising the stepsof: (a) encoding media data; and (b) multiplexing the media data encodedin the step (a) in units of a predetermined frame, and inserting asecond flag having a predetermined length with an auto-correlation inthe frame after a first flag having the opening and closing of theframe.

[0005] Preferably, the second flag of the step (b) has a bit pattern of“10110010”.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The above object and advantages of the present invention willbecome more apparent by describing in detail a preferred embodimentthereof with reference to the attached drawings in which:

[0007]FIG. 1 is a schematic block diagram of a device for implementing amultiplexing method for multimedia communication, compatible with theH.223 protocol, according to the present invention;

[0008]FIG. 2A is a diagram showing the structure of a general H.223MUX-PDU frame; and

[0009]FIG. 2B is a diagram showing the structure of an H.223 MUX-PDUframe according to the present invention;

[0010]FIG. 3A is a diagram showing the structure of the H.223 MUX-PUDframe in a filling mode; and

[0011]FIG. 3B is a diagram showing the structure of the H.223 MUX-PUDframe in an abort message mode.

DETAILED DESCRIPTION OF THE INVENTION

[0012] In FIG. 1 showing a device for implementing an H.223 multiplexingmethod for multimedia communication according to the present invention,a multiplexing portion 130 includes an H-223 protocol unit 110 and atranscoder 120. The H.223 protocol unit 110 and the transcoder 120performs multiplexing with respect to encoded media data (video, audioand other data), passing through protocol data units (not shown) totransmit to a channel.

[0013]FIG. 2 is a diagram showing the structure of a general H.223MUX-PUD frame.

[0014] As shown in FIG. 2A, the H.223 MUX-PDU is constituted by units ofa frame, and the frame includes a high-level data link control (HDLC)flag 110 for transmission control, a header 120 including datainformation, and a payload 130 including video and audio data.

[0015] All MUX-PDU of the H.223 are defined using the HDLC flag 110 ofFIG. 2A. The HDLC flag 110 has an unique bit pattern “101111110” havingsix continuous “1s” representing the opening or closing of the frame,and is used for synchronization of the frame.

[0016]FIG. 2B is a diagram showing the structure of an H.223 MUX-PDUframe according to the present invention. The MUX-PUD frame includes anHDLC flag 140, an extra flag 150, a header 160 and a payload 170. Thetranscoder 120 inserts an θ-bit extra flag 150 which is similar to apseudo noise code (PN CODE) having a high auto-correlation next to theHDLC flag 150 as shown in FIG. 2B. Here, the reason for selecting theextra flag having a bit pattern of “10110010” is due to its highauto-correlation as the PN CODE does. Thus, only the bit pattern of“10110010” may be added as the extra flag 150, or other bit streamshaving a high auto-correlation may be used thereas to increaseerror-resiliency. Also, a longer flag may be added in consideration of atrade-off with a channel band width. Preferably, adding the extra flag,suggested by the present invention is used, is prevented in a fillingmode in which HDLC flags exist continuously as shown in FIG. 3A or anabort message mode without having a payload as shown in FIG. 3B.

[0017] The multiplexing method for multimedia communication according tothe present invention is not limited to the particular forms illustratedand further modifications and alterations will occur to those skilled inthe art. That is, interleaving and RCPC processes may be performed byusing each extra flag of a plurality of MUX-PDUs.

[0018] As described above, in the multiplexing method for multimediacommunication according to the present invention, MUX-PDU including anextra flag having a high auto-correlation is transmitted in the H.223protocol, increasing the probability of detecting the MUX-PDU by areceiver. Thus, error-resiliency is also increased. Also, when themultiplexing method is used together with the RCPC and interleavingmethods, error-resiliency can be further increased.

What is claimed is:
 1. A multiplexing method for multimediacommunication in the H.223 protocol, comprising the steps of: (a)encoding media data; and (b) multiplexing the media data encoded in thestep (a) in units of a predetermined frame, and inserting a second flaghaving a predetermined length with an auto-correlation in the frameafter a first flag having the opening and closing of the frame.
 2. Themultiplexing method of claim 1 , wherein the frame further comprises: aheader having data information: and a payload having video and audiodata.
 3. The multiplexing method of claim 1 , wherein the second flag ofthe step (b) has a bit pattern of “10110010”.
 4. The multiplexing methodof claim 1 , wherein the second flag of the step (b) is a pseudo noisecode (PN CODE).
 5. The multiplexing method of claim 1 , wherein themultiplexing of the step (b) is performed together with an interleaving.6. The multiplexing method of claim 1 , wherein the second flag isinserted in the frame when a plurality of the first flags existcontinuously or no payload exists in the frame.